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1520D - Same Differences.cpp
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1520D - Same Differences.cpp
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/** ========================================**
** @Author: Kareem Taha Abdelfatah
** @Category: Codeforces problems solutions
/** ========================================**/
#include<bits/stdc++.h>
#include<iterator>
using namespace std;
#define IO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define endll "\n"
#define ll long long
#define fr(i, n) for(ll i = 0; i < n; i++)
#define fr1(i, n) for(ll i = 1; i <= n; i++)
#define asort(a) sort(a + 1, a + n + 1)
#define dsort(a) sort(a + 1, a + n + 1, greater<int>())
const long long N = 2e5 + 5, MOD = 1e9 + 7, oo = 1e18;
const double PI = 3.14;
const double Prox = 1e-7;
map<ll, ll>mp;
ll a[N];
int main()
{
IO
int tc; cin >> tc;
while(tc--){
mp.clear();
ll n, ans = 0; cin >> n;
fr1(i, n){
cin >> a[i];
mp[a[i] - i]++;
ans += mp[a[i] - i];
}
cout << abs(n - ans) << endll;
}
return 0;
}